A sealing device of the type referred to in the preamble is known for instance from U.S. Pat. No. 4 284 264. This known device comprises a homogeneous sealing ring intended to be mounted in a slot in the valve housing. The valve ring cross-section is an elongated flat body. The ring normally consists of metal and is considerably rigid with respect to deformation in the radial direction. The ring may, however, be bent aside by the throttle, when the throttle is pressed against the sealing ring. The inner, bluntly rounded edge of the ring constitutes the second sealing surface referred to above. A pair of spring washers are pressed against the two flat sides of the sealing ring, and between these two washers is formed the slot in which the sealing ring is mounted. The spring washers are in turn arranged between the valve housing and a mounting ring, gaskets being placed between the latter parts and the spring washers. Although this known device has several positive qualities compared to prior art and has signified a substantial improvement within this particular field, the two spring washers and the gaskets do constitute a complication.
From for instance U.S. Pat. No. 3 080 145 and U.S. Pat. No. 4 058 290 the use of sealing washers with a U-shaped section is known for throttle valves with metallic sealing. In comparison with U.S. Pat. No. 4 284 264 these have the advantage of being uncomplicated and not requiring separate gaskets. On the other hand, they have a low rigidity and resistance to radial deformation, which is unsatisfactory at least for some applications.